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Author Topic: DC Battery Banks  (Read 12999 times)

GuyFawkes

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DC Battery Banks
« on: October 19, 2006, 04:52:21 PM »
take two 12vdc 100 Ah lead acid batteries, wire them in parallel and you get 12 vdc and 200 Ah, wire them in series and you get 24vdc and 100Ah.

Got a quote for a guy today for some dc battery banks, these are UK pound Sterling prices.

This is for a 48 vdc bank of 1000 Ah made up from deep cycle traction cells, they are premium military quality (hawker) and will last 20 years, doing it this way means you can add blocks of 1000 Ah at a time as capital allows, and they all mix and match easily. Each bank is large enough that provided you keep them off the ground and away from frost you don't have to worry about battery temperature.

So, a 48 vdc 1000 Ah bank (each cell is 570 h x 555 l x 198 w (mm of course) will weigh 1287 Kg and cost UK Pounds £1893.32 ex VAT (17.5%)

In the UK it will cost you that much to tie in to the grid, and for that you get 1000 Ah @ 48 vdc

Since in DC W = V x A that works out about 48 KWh, enough for anyone.

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twombo

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Re: DC Battery Banks
« Reply #1 on: October 19, 2006, 07:06:16 PM »
"enough for anyone."

Yeah,  I only use 1.6 kW per day, at my home. My inverter only takes about 20 minutes in absorbtion charge before it goes into float.   About enough time to pump a couple hundred gallons of water or do one load of laundry.  Then the peace and quiet returns.

A Lister or Petter driving a 24 volt DC alternator is my end goal. A mini Petter would probably do it, but a Lister probably would be better for co-generation.

Guy_Incognito

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Re: DC Battery Banks
« Reply #2 on: October 19, 2006, 07:15:24 PM »
Not too bad, Guy_F. The price is pretty good.

What's the configuration of the bank - 20 x 2V 1000Ah cells?

The theory is that you shouldn't mix and match various ages of lead-acid cells , as they all wind up differing Ah capacities as they age, so one set will tend to cop it more when charging/discharging. In practice, well, worse things happen to batteries....

48kWh is a fair old chunk of storage - any specs on how hard you can cycle them?
Eg, sonneschein (sp?) gel cells are rated for 500 x 100% deep cycles before they're down to 80% capacity. You average car battery can probably do 5 or 10 100% cycles before it's stuffed.

Probably end up with 30kWh usable capacity (70% discharge) or so out of one of those packs if you want to get decent life from them.

Looking at getting a set of nickel-iron cells for the off-grid place I'm slowly building. 400Ah each at 1.2V.... probably 40 in series/parallel to get about 24V / 18kWh storage. As a guide to price - that's about $10,000 delivered in Australia. Nickel-iron's pretty lossy on the charge side of things, but their advantage is that they're pretty much indestructible and you really can mix and match cells with impunity. That 18kWh storage will run the large system there for about 4 or 5 days at 4kWh a day.

GuyFawkes

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Re: DC Battery Banks
« Reply #3 on: October 19, 2006, 07:35:57 PM »
They are real heavy duty premium quality, designed for daily charge / discharge cycles down to 80% discharge driving bad loads on electric vehicles with lets be honest less than ideal maintenance and enviornments and still give a minimum 5 year working life, in a domestic set up, clean enviornment, monitored properly you'll get nearer 20 years, and after 5 years you can add another bank and they won't be so mismatched as to worry.

2 quid per ampere hour is about right for top quality traction lead acids.

48vdc is a telecomms voltage, so nice trade between resistance losses etc.

Point is these are real numbers, and you work out at about ballpark 50KWh of reserve capacity, always on, always ready, always silent power for the same money as a grid tie for generation resale here in the UK.

It's a no brainer.

The batteries themselves are EPzS series, a non brainer, as the 48 vdc 1000 Ah spec is very popular with electric vehciles so they are made in some volume and you get the economies of scale.

====================

My mate who bought the start-o-matic asked me a few days ago about DIY building batteries, I asked this old boy about it today, he used to do it in the sixties, no fucking way it was commercially viable nowadays, he said you could buy ready made chinese batteries cheaper than you could buy the bare lead and zinc plates today, economies of scale and all that.

When he started a good quality car battery was three pounds and ten shillings, which was ten shillings more than his weekly wage....
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3Kw 130 VDC Dynamo to be added. (compressor + hyd pump)
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Current status - project / standby, Fuel, good old pump diesel.

Guy_Incognito

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Re: DC Battery Banks
« Reply #4 on: October 19, 2006, 08:34:32 PM »
Sounds like they're pretty good spec then.

And you're right about the chinese - they make a lot of things so cheap that it's not worth the time and effort to do it yourself (or locally). Which is a great pity really.

kingmanbob

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Re: DC Battery Banks
« Reply #5 on: October 20, 2006, 10:29:16 PM »
"enough for anyone."

Yeah,  I only use 1.6 kW per day, at my home. My inverter only takes about 20 minutes in absorbtion charge before it goes into float.   About enough time to pump a couple hundred gallons of water or do one load of laundry.  Then the peace and quiet returns.

A Lister or Petter driving a 24 volt DC alternator is my end goal. A mini Petter would probably do it, but a Lister probably would be better for co-generation.

Just make sure you use a "smart" 3 stage external regulator such as the Balmar Max-Charge.
Set the amp manager to 80%. Use the temp probe for temperature compensation.

I burned up a lot of alternators, and ruined a lot of batteries before I learned this!

Bob

rcavictim

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Just scored a battery bank
« Reply #6 on: October 31, 2006, 12:21:46 AM »
I was most fortunate to obtain a carload of sixteen, Hawker, SLA 105 AH, 12 volt batteries today freshly decommissioned out of a telco plant. I have a buddy on the inside.  They were apparently tested to still have something like over 60% of their capacity left and all look in perfect shape with no nasty case bulging which I`ve become accustomed to seeing in well used surplus batteries that get passed on down the food chain to fellas like us.  ;)  They all measured around 12.4 volts and have been off float, just sitting for about two weeks. They weigh 97 lbs. each and the poor car was completely bottomed out on the long drive home.  No problems en route and the batteries are now safely unloaded into my shop.  I lugged two of them to my house to experiment with on a 1000 watt Xantrex 12 volt inverter.  I want to see what these batteries have in them for remaining capacity.

These are a Espace Hi 12 Hi 105.  Made in France by Oldham.  I am having trouble finding info on them.  I suspect they are not gell cells but rather the wet cell technology that uses liquid acid in a fiberglass wool like structure to prevent spilling.  I believe this type of battery would be more amenable to the pulse type desulfation gadgets now available and I would like to explore this technique in order to try to increase the capacity and remaining lifetime of my *new* battery bank.

So if I am down to 60% capacity I have 1008 AH at 12 volts.  That`ll run a 1 kW load for 12 hours.  That`s a good start.  ::)  If I can recover more through pulsing, that will be awesome!
« Last Edit: October 31, 2006, 05:19:02 AM by rcavictim »
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DaveW

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Re: DC Battery Banks
« Reply #7 on: October 31, 2006, 02:18:48 AM »
   RCAV-
     I would move very slowly regarding pulsing AGM batteries.  I have three sets of 48volt Absolyte AGM batteries, and they are picky about charge voltage set points.  I would try some charge/discharge cycles first to see if these pick up any first.  In my experience telco sets tend to run charge cycles too long without any interstitial discharge, and batteries can sometimes be brought back with a few cycles down to 80% or so over a few days.  Then if needed apply only very short duration pulsing to try to cure the sulfation.  What you have is a great find, it would be a shame to cook them without first trying standard recovery techniques.  I have tried de-sulfation on some large traction batteries with reasonable luck, but they were just about gone when I got them so I was willing to try anything at that point.  The key to AGM technology is accurate cell voltages and temperature monitoring.

rcavictim

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Re: DC Battery Banks
« Reply #8 on: October 31, 2006, 02:35:19 AM »
DaveW,

Thanx for the advice.  I plan to be gentle with these.  You are right.  Precious score!  At least I have some basic valuable info printed on the label like 105 AH at 8 hour rate @ 25 C., and a chart showing accurate float voltages versus temperature, and that 10.5 volts is the bottom limit for discharge (which seems to be pretty standard for gell cells I`m seeing in similar service).  I also note that the Xantrex inverter is factory set to shut down at 10.5 volts.

On your double post, just delete the second one.  Might have been a cosmic ray.
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Chaz

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Re: Just scored a battery bank
« Reply #9 on: November 03, 2006, 07:59:01 PM »

So if I am down to 60% capacity I have 1008 AH at 12 volts.  That`ll run a 1 kW load for 12 hours.  That`s a good start.  ::)  If I can recover more through pulsing, that will be awesome!
FYI - putting more than two batteries in parallel is a bad idea. Paralleling this many is a very bad move. Certainly they will work, but you're asking for trouble.... sorry.
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haganes

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Re: Just scored a battery bank
« Reply #10 on: November 04, 2006, 03:59:40 AM »

FYI - putting more than two batteries in parallel is a bad idea. Paralleling this many is a very bad move. Certainly they will work, but you're asking for trouble.... sorry.
Quote

could you please provide some facts to support this??

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rcavictim

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Re: Just scored a battery bank
« Reply #11 on: November 04, 2006, 01:53:37 PM »

So if I am down to 60% capacity I have 1008 AH at 12 volts.  That`ll run a 1 kW load for 12 hours.  That`s a good start.  ::)  If I can recover more through pulsing, that will be awesome!
FYI - putting more than two batteries in parallel is a bad idea. Paralleling this many is a very bad move. Certainly they will work, but you're asking for trouble.... sorry.

Let me be clear that any setup I might cobble together which involves multiple batteries in parallel will employ a series protection fuse between each battery and the main buss.  Without such fuses a short circuit fault in one battery would have to carry the current produced by all the rest of the batteries.  This could result in a really bad day, extensive property damage or worse.

I am researching the possibility of combining a even number of those inexpensive 12 volt mod-sine inverters to operate with their primary circuits in series to allow operation on a 48 volt (or higher) battery bank.    High DC voltage inverters in the 4 kW and higher class are quite prohibitively expensive.
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listerdiesel

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Re: Just scored a battery bank
« Reply #12 on: November 04, 2006, 05:09:11 PM »

FYI - putting more than two batteries in parallel is a bad idea. Paralleling this many is a very bad move. Certainly they will work, but you're asking for trouble.... sorry.

Not necessarily, it is done a lot commercially, but with steering diodes in each string so that they cannot discharge into each other and walk the capacity down. It works if both batteries are exactly the same capacity and internal impedance, which they never are :-))

It is almost as much of a problem on 110V batteries to keep the cells all in balance, but most of these are on float charge all the time and have sufficient time to equalise.

We are fitting new 110V 200A battery sets into substations at present, next one arrives Monday, we take out the old ones for recycling. The new batteries are vented lead-acid with recombination filler/vents to trap any gasses and turn them back into water which runs back into the battery.

Peter
 

buickanddeere

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Re: DC Battery Banks
« Reply #13 on: November 08, 2006, 02:26:26 AM »
  A battery bank should be floating isolated from ground. Contact with a "live terminal" will not draw an arc or give you a shock. Trouble is to maintain the float. Lead acid batteries fume and blubber. The resulting conductive salts on the battery case will track current. The higher the voltage, more tacking.
   If you've ever been bitten by 120VAC  and  120VDC. The DC shock seems to worse. Particularly working around batteries as your hands maybe damp and covered with salts.   
  48V battery banks are popular for a reason. 

Andre Blanchard

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Re: Just scored a battery bank
« Reply #14 on: November 14, 2006, 10:14:11 PM »

FYI - putting more than two batteries in parallel is a bad idea. Paralleling this many is a very bad move. Certainly they will work, but you're asking for trouble.... sorry.
Quote

could you please provide some facts to support this??

captain steve

I have a 12 volt pack for the house, PV and wind system.  I am currently running in scrounge and recycle mode on the pack saving money and time to get a quality pack.

Anyway being as it is a mixed pack of older batteries they need watching, two weeks ago I noticed the voltage was dropping off faster in the evening, it happens this time of year anyway as the days are shorter and more clouds, but this seemed more then normal.  A week ago I noticed that one battery was running hotter then the rest and would start to boil with any significant amount of charging.

So I remove that battery from the circuit and put a volt meter on it and watched as it quickly dropped to about 10.5 volts.  Tells me the battery has a shorted cell resulting in it hogging most all of the charging current while not contributing anything on discharge in fact the rest of the batteries were being discharged all night long holding this one battery at a high float charge voltage.

Pack performance has improved a lot since that battery was removed.  A few days later I checked the voltage on the bad battery again only to find that it had dropped to 8 volts, so a second cell was also on its way out.
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